Hydraulic hammers are used on work sites to break up large hard objects before such objects can be moved away. Hydraulic hammers may be mounted to back hoes or excavators or other machines. Typically, the hammer assembly is powered by either a hydraulic or pneumatic pressure source or a combination of both. With those hammer assemblies powered by a combination of hydraulic and pneumatic pressure, a piston is retracted against a volume of compressible gas by applying a hydraulic fluid pressure to a first shoulder of a piston. As the piston retracts, the volume of gas decreases, increasing its pressure. Once the piston reaches a predetermined position, high pressure hydraulic fluid is applied to a second shoulder of a piston that drives the piston in a downward direction for a work or power stroke. The downward movement of the piston allows the compressed gas to expand, releasing energy which further propels the downward movement of the piston. During the power stroke, the downward moving piston strikes a work tool, which, in turn, is driven in the downward direction. The work tool strikes the object to be broken up.
Hydraulic hammers may be used to break-up a variety of materials such as rock, concrete, asphalt, or other hard objects. The physical properties of these materials can vary. For example, some materials may be harder than others. Harder materials typically require higher impact energy to fracture. One way to deal with this issue may be to use the hammer for a longer period of time on such materials. Another may be to switch to larger, more powerful hammers when encountering harder materials. However, both of these methods are inefficient and time-consuming. Moreover, while some hydraulic hammers have external, manual adjustments that can be used to shorten the length of the piston stroke, such adjustments do not allow for any increase in impact energy. To the contrary, while shortening the length of the piston stroke increases the frequency of the hammering, it decreases the impact energy produced by each stroke of the piston. Additionally, increasing the charging pressure of the compressible gas chamber in order to increase the impact energy produced by the hammer may undesirably shorten the life of the seals associated with the gas chamber as higher gas pressures are generally harder on the seals.